Production of zein



Oct'. 19, 1943.A Yl.. c. s'wALLEN E1' AL A2,332,356

PRODUCTION oF zEIN Filed Aug. 5, 1940 wmp 2- @Mama-faz) 0MM/a2@mg/Miedo?- Patented Oct. 19, 1943 PRODUCTION F ZEIN Lloyd C. Swallen..Villa Park, and Martin L.

Ill., assignors to Corn Products Refining Company, New York, N. Y.,acorporation o! New Jersey Application August v3, 194o, seria1 No.'350,532

Hamilton, Berwyn,

'11 Claims.

This invention relates to the production or treatment of nein, thealcohol soluble constituent of corn (maize), gluten, for the purpose ofimproving the quality of the zein in two respects particularly: improvedsolubility characteristics and increased -solution stability. Improvedsolubility is evidenced by reduction in insoluble protein and lowercloud point.

For purposes of comparison the solubility of.

the zein, asv discussed herein, will be measured, negatively, bydetermination vof the amount of insoluble proteins, precipitated when 1gram of zein is dissolved in 100 c'c. of ,92%. by volume, ethyl alcoholat 25 C. Y

'Ihe cloud point of the zein, which is also a measure of solubility, isdetermined by dissolving l. gram. of zein in 5 cc. of 95% by volumeethyl alcohol, cooling the solution until denitely turbid, then allowingthe solution to warm while stirring with a. thermometer until the solution becomes homogeneous. The temperature thus obtained is corrected toa inal alcohol concentration in a solvent of 93%, by volume, by means ofappropriate correction factors which take into consideration themoisture content of the zein. The temperature at which the solutionbecomes homogeneous from a condition of turbidity, or vice versa frombeing clear begins to become turbid is called the cloud point.

'Ihe solution stability tests are made as follows: zein equivalent to 9grams or protein is dissolved in 25 cc. of 95%, by volume, ethyl.alcohol. Sumcient water is added to reduce the alcohol concentration,taking into consideration the water content or the zein, to 91%, byvolume. The resulting solution is placed in two test tubes approximatelyit nim. in diameter and 12 cm. long. The tubes are lle'd to such aheight that a bubble about l. cm. long remains.- One of the tubes isstored at 25 C. and another at 50 C. At appropriate intervals theviscosities are determined at 25 C. (the 50 sample being cooled to 25for this test) by inverting the test tubes and.

l noting the time in seconds required for the air bubble to make its Waythrough the zein. The end points in these tests, reported as days forexample, are when the viscosity attained in the 50 test is 15 secondsand in the 25 test is 20 seconds.

These tests are purely arbitrary and other tests giving, in comparison,equivalent results, might be employed for determining the solubility ofthe lzein, as produced or treated in accordance with the presentinvention, and the stability of it solution.

The improvements in the quality of the zein in accordance with thepresent invention are effected by introducing into a solution of thezein, for example, into the extract from Ithe gluten meal at any stageof the process or into the gluten meal undergoing extraction, analkaline substance.

The alkaline substances which may be used in this connection includesodium, potassium, ammonium and calcium hydroxides, sodium and potassiumcarbonates, and other alkaline materials of similar nature. The use ofbarium hydroxide is possible but is less effective because it combineswith the zein to form salts which, or some of which, are less solublethan the untreated zein. Allalkaline substances may be used more or lesseiectively.

The solutions treated in accordance with the present invention may besolutions in which the zein is dissolved in any of the common zeinsolvents in which the solvent is not chnically reactive with the zein oralkali; those, for example, as are ordinarily used in the extraction ofthe zein from gluten meal, such as ethyl alcohol or isoproply alcohol. V

The invention is applicable, when used in connection with the extractionof the zein from its raw material, to either a strong alcoholicextraction, employing, say, to 92% isopropyl alcohol (or to 95% ethylalcohol) or to an extraction process using more dilute alcohol such as55%-65% isopropyl alcohol (or 55%-70% ethyl alcohol). .These two typesof extraction process do not produce zein having exactly the samecharacteristics. The process using dilute alcohol extracts fractions notremoved when a more concentrated alcohol is used and gives a zein ofless solubility, when dissolved in more concentrated alcohol, and ofreduced stability in lcomparison with the product of the strongeralcohol extraction. There is, therefore, a distinct advantage in usingthe expedient of the present invention in connection with an extractionprocess employing a weak alcohol. By treatment of the zein, thusobtained, with an alkali the relatively poor quality zein obtained bythe weak alcohol may be improved so as to compare favorably with thezein extracted by strong alcohol. There is a more or less criticaldistinction between the two processes: the processes using strongalcohol require an oil and color removing operation which is notnecessary with the processes using weak alcohols. The latter processesare,4 therefore, cheaper but give a poorer quality of zein which,however. can be improved in accordance with the present invention.

process, but in such case the introduction should be, preferably atleast, in advance of a ltering step in order that substances orcompounds precipitated by the alkali treatment should be removed fromthe solution. It is also preferable in case the alkali is introducedinto the extract after the extracting operation to subject the zeinsolution to an ageing operation in the presence of the alkali tocompensate for the high temperatures prevailing in the extracting step.

Where the improvement of the present invention is used in connectionwith a process of extractioninvolving ultimate precipitation of the zeinfrom an alcoholic solution by the addition of large volumes of Water, itmay be desirable to add enough acid to the zein solution, afterfiltration, yto prevent the formation of emulsions in the precipitatingvessel. Approximately one-half of the alkali may be neutralized in thismanner without nullifying, to any substantial extent, the beneficialresults of the alkali treatment in the respects above noted. Where thealkali is added to the extraction step, the quantity is preferably suchas to give ythe extract a pH of 9 to 11.5, or slightly higher than this.The amount of alkali added at this stage of the process, in order to getthe same results, should be greater than the amount added at laterstages of the process since the non-zein constituents of the gluten mealtake up a certain amount of alkali.- Hence, there are advantages intreating the extract with the alkali instead of the material beingextracted. The combined improvement in solubility and stability of thesolution is not obtained in a practical degree by the use of alkali inlesser amounts than are required to give the extract or other solutiona-pH of 9 or higher. On the other hand, if the pH is substantiallyhigher than 11.5, no additional benefits result and there is danger ofdegrading the zein chemically.

Where the zein is separated from the alcohol by precipitation in Water,the amount of alkali used should not, ordinarily, be great enough togive a pH to the precipitating Water solution higher than 10; o r the pHshould be reduced at this point to 10, or below, by the neutralizationof some of the alkali by means of an acid, as referred to above.

The eiect of the alkali, particularly in the solutions or extracts ofhigher alcohol concentration, appears to be to bring a precipitation ofprotein bodies which are relatively insoluble in the higher alcoholconcentrations, and these bodies are consequently removed by ltration.The second effect is to increase the solubility of certain proteinfractions in a dilute aqueous alcohol of the concentrations which.prevail in the usual precipitating operations or such as prevail when a'controlled amount of water is added to precipitate the larger portion ofthe zein in an essentially fluid state. The latter forml ofprecipitation is largely used in the low alcohol extractions. The alkaliby increasing the solubility of these fractions in the aqueous mediumprevents their precipitation. The third effect seems to be a permanentsolubilizing of the zein.

vassiste In the accompanying drawing:

Fig. 1 is a flow sheet illustrating the application of the presentinvention to a known process of extracting zein with a highconcentration of alcohol, in which process the alkali, used inaccordance with the present invention, is introduced at the extractionstep.

Fig. 2 is a flow sheet illustrating a process us- `ing alcohol of lowconcentration in which process the alkali is added to the extract duringor after cooling, and the solution aged, and subsequently filtered.

The flow sheets will be referred to in connection with the followingspecific examples'of the application of the invention to practice. Itwill be understood that these examples are to be considered asinformative and typical merely and not as limiting the invention to theparticular operating data given; the intention being to cover allequivalents and also all modifications within the scope of the heretoappended claims. The f'lgures in vparentheses indicate practical ranges.

Example I-Fz'g. 1.--400 grams of gluten meal, 1300 ec. of 85% isopropylalcohol (80% to 92%) and 7.7 grams (6 to 14 grams) of sodium hydroxideare agitated inthe extraction vessel I at 60 C. (50-65 C.) for 11/2hours. The pH of the extract from the extraction vessel is about 10 (9to 11.5). The extract is cooled at 2 to 15 C. and filtered at 3. Thefiltered solution is run into a mixing vessel 4 into which is introducedan equal volume of hexane, or other solvent of oil and coloring matter;and the hexane, oil and color, with some alcohol, are separated from theheavy alcohol-zein solution at 5. The hexane with its contents is sentto 'the recovery system which forms no part of the present invention.The heavy zein-alcohol solution is heated at 6 with the introduction ofalcohol vapors and the residual hexane removed in the solvent flasher 1.The zein is separated from the alcohol in the precipitation vessel 8, bythe addition to the solution of large amounts of water, and the zein isfiltered and dried at 9.

The above process steps, except for the introduction of the alkali, aredisclosed in applications for United States patents to Anthony C. Horesiet al., Serial No. 214,512, filed June 18, 1938, (Patent No. 2,238,591,April l5, 1941) and of Lloyd C. Swallen, Serial No. 240,307, filedNovember 14, 1938, (Patent No. 2,287,649, June 23, 1942) Serial No.155,691, led July 26, 1937, (Patent No. 2,221,560, November 12, 1940)and Serial No. 313,671, filed January 13, 1940 (Patent No. 2,221,561,November 12, 1940). These applications for patent describe processeswhich are now 1n use.

A product made in accordance with this invention, as just described,employing the preferred operating data given above, contained 1.94% ofinsoluble protein; had a cloud point of 5.5 C., astability of 72 days at25 C., and a stability of 23 days at 50 C. A correspondingly madeproduct, without the use of the alkali, had an insoluble protein contentof 4.38% a cloud point of 23 C., a stability at 25 C. at 22 days, and astability at 50 C. at 13 days. This gives an indication of theimprovements in the quality of the zein brought about by the use of thepresent invention.

Example 2-Fig. 1.-The process is the same as in Example 1 except that 12grams of sodium r hydroxide, instead of '7.7 grams is introduced intotered solution from iilter 3 a pH of 10.4; and suiicient acetic acid isadded (as shown by the dotted line arrow) to the clariiied extract at 4to neutralize apprcximatelybne-hali of the alkali originally added.

A product made by the process o! Example 2 had an insoluble proteincontent of 1.34%, a cloud point of 15.5 C., a stability of 80 days at 25C. and a stability of 85 days at 50 C.

Example 3-Fig. 1.-A zein solution is prepared by extracting gluten mealwith 85% isopropyl alcohol for 1% hours at 60 C., as in the previousexamples but without introducing alkali into the extraction vessel.

The resulting solution is adjusted to a protein content of approximately6 grams of protein per 100 cc. To this extract, before clariication, isadded sodium hydroxide (as4 indicated by the dotted arrow at 2),amounting to 0.2 gram per 100 cc. of the solution. This gives thesolution a pH of 11.5. After clarification suicient hydrochloric acid isadded to the mixing vessel 4, as shown by the dotted arrow, toneutralize half of the above stated amount of alkali. 'Uponprecipitation with water, which yielded a water phase having a pH of6.8, a sample of the zein, obtained in accordance with this example, wasanalyzed and had an insoluble protein content of 0.87%, a cloud point ot18.5%, a stability of 8 days at 25C., and a stability of 16 days at 50C.

Example 4-Fig. 2.-The gluten meal is Yextracted in the extraction vesselI by isopropyl alcohol of 60% by volume concentration (55%- 65%) for 1%hours at 60 C. Similar results can be obtained by using ethyl alcohol at55%-70% concentration by volume. The extract, having a concentration of7.14 grams of protein per 100 cc. of the extract, is run into a vesselII and is there treated with 1.5 grams of sodium hydroxide per 100 cc.of extract. The mixture which has a pH of 9.0 is aged for 1 hour at roomtemperature. The material is then cooled to 15 C. at I2, filtered at I3,and water added at I4 to reduce the alcohol content to about 35%, byvolume. At this point the zein is separated as a heavy solution, the pHadjusted by addition of acid at I5, (an optional step), and the zeinprecipitated at I6 by the addition of large volumes of water. 'I'heprecipitated zein is'iiltered and dried at I1. 'I'he alkaline substancemay be introduced at any suitable stage of the process, for example inthe extraction stage. n

A product obtained from the process in accordance with Example 4 had aninsoluble protein content of 2.5%, a cloud point of 14.5 C., a stabilityat 25 C. of 10 days, andl a stability at 50 C. of 1 day. Under the oldprocess where the alkaline substance is not used, a common insolubleprotein content is about 15%.

Example Fig. 2.-The process is the same as in Example 4 except that theextract is treatedl with 2.3 grams of potassium hydroxide per liter ofextract. This will give the mixture a pH of about 9.9. After ageing for16 hours at room temperature, the extract is worked up as in Example 4.

A product made in accordance with Example 5 had an insoluble proteincontent of 1.2%, a cloud point of 17 C., a stability at 25 C. of 31days, and a stability at 50 C. of 3 days.

Example 6-Fg. 2.-The process here is the same as in Examples 4 and 5,except that the extract is treated with calcium hydroxide in theproportion of 3 grams of calcium hydroxide per liter of extract. Thisgives a mixture having a pH of 11.3. After ageing for. 18 hours at roomtemperature, and recovery of the zein as in Examples 4 and 5, theproduct had an insoluble protein content of 2.5%, a cloud point of 15.5C., a stability at 25 C. o! 20 days, and a stability of 50 C. of 1 day.l

The products oi the above described invention, as described in Examples1 'to 3, when subjected to the tests above described, are characterizedby high solubility, e. g. 0.5% to 2.5% insoluble substances; ylow cloudpoint, e. g. 5 to 20 C.; and high stability, e. g. 40 days to 85 days at25 C., and 8 days to 85 days at 50 C. The zein treated in accordancewith the present invention is somewhatlighter in color than ordinaryzein.

The relatively low stability ci the-products of Examples 4 to 6 is noindication of failure ci the process since the extracts obtained withthe low concentration alcohols of these examples 'give zein solutionswhich are very unstable in comparison with solutions obtained byextraction with high concentration alcohol. In Examples 4 to extractionprocess in an amount to give th-solution a pH ofsubstantially 9 to 11.5;andfremoving precipitated matter.

2. Improvement in the process of extracting zein from gluten meal withan alcoholic solvent and recovering the zein from the solutionwhichcomprises: introducing a small amount of an alLaline substance intothe zein undergoing extraction to give the extract a pH ofsubstantially9 to 11.5; and removing precipitated matter.

3. Improvement in the process of extracting zein from gluten meal withan alcoholic solvent and recovering the zein from the solution whichcomprises: introducing a small amount oi' an alkaline substance into thezein extract and filtering the extract'to remove precipitated proteinbodies.

4. Improvement in the process of extracting zein from gluten meal withan alcoholic solvent and recovering the zein from solution byprecipitation with water, which comprises: bringing into contact withthe zein extract an amount of a1- kaline substance to give the extract apH of approximately 91'1.5; removing from the extract protein bodiesrendered insoluble by said alkali treatment; and, before precipitatingthe zein with water, neutralizing with an acid a part only of thealkaline substance so as to prevent formation of emulsions whenthe zeinis precipitated in water.

5. Improvement in the process of extracting zein from gluten ineal withan' alcoholic solvent and recovering the zein from the solution byprecipitation in water which comprises: introducing a small amount of analkaline substance into the zein extract; ltering the extract to removeprecipitated protein bodies; and treating the zein solution with an acidto neutralize part only of said alkaline substance before the solutionis subjected to the precipitating step for the purpose of preventing theformation of emulsions during the precipitating step.

6. Process of obtaining zein from gluten meal which comprises:extractingthe zein with an al- -zein from gluten meal by stantia 9-11.5;cooling the extract; filtering the extract to remove precipitatedprotein bodies;

. introducing an acid into the filtered solution to neutralize aboutone-half of the alkaline substance; and precipitating the zein from itssolution by the addition of large volumes of water.

7. The process of claim 6 in which the sodiuml hydroxide is introducedinto the zein extract before the filtering operation instead of into theeX- traction step.

8. Process of obtaining zein from gluten meal which comprises:extracting the zein with an a1- coholic solvent; adding to the extract asmall amount of an alkaline substance and ageing the mixture; iilteringthe zein solution; adding acid thereto to neutralize a part only of thealkaline substance for the purpose of preventing the formation ofemulsions during the precipitating step; and precipitating the zein fromthe solution by water.

9. Improvement in the process of obtaining extraction with an alcoholicsolvent which comprises: adding a small amount of alkaline substance tothe extract to precipitate protein matter; ageing the extract at tainingmaterial subjected to the process an amount of an alkaline substance togive the extract a pH of approximately 9-11.5 so as to increase thesolubility and solution stability of the product without degrading thezein chemically; and removing precipitated protein matter from theextract.

' 11. Process of improving the solubility and solution stability of zeinwhich comprises: treating a solution of the zein in a solvent notchemically reactive with zein or alkalies at a temperature substantiallywithin the range of err-65 C. with an amount of alkali to givethesolution a pH substantially within the range 9-11.5 to precipitateprotein matter and to solubilize additional protein matter withoutdegrading the zein; and removing the precipitated protein matter.

LLOYD C. SWALLEN. MARTIN L HAMILTON.

CERTIFICATE. or CORRECTION.

Patent No. 2,552,556. october 19,l 191+5.

LLOYD- C.SWALLEN, ET AL'.

1t is hereby certified that error appears in the printed specificationofthe above numbered patent requiring correction as follows: Page h,first column,` lines 26 and 2"( claim 9, fqr extract-to precipitateproteinmatter;

ageing the extract at read--extractg ageing the extract to precipitateprotein matter ath; and that the said Letters Patent should be read withA'mis correction therein that the: same may conform to the record ofthevcase in the Patent Office.'

signed and sealed this 21st day 'of December, A. D. 19u5.

Henry Ven Arsdale,

(Seal) f hating C'ommi'ssioner of Patents.

